Issue 585:
PDFium always uses /Rect coordinates to annotation

Issue description

I have been investigating some differences in the way PDFium and
Acrobat draw some annotations.
One difference is clear:
On Acrobat, if "/AP" is present on the "/Annot" definition, the
coordinates used to draw annotations come from "/Rect"
values. On the other hand, when "/AP" is not defined, "/QuadPoints" is
used to grab the annotation coordinates from.
The divergence comes from the fact that PDFium uses "/Rect" regardless
the presence or absence of "/AP".
This might cause differences on where annotations are placed in
Acrobat reader and on PDFium, depending on whether /Rect and
/QuadPoints values differ.
For instance, here is an example:
- open the following PDF samples [1] and [2] in Acrobat (side by side
is better), and compare the placement of the annotation in each case.
Then do the same with PDFium (e.g. using Chromium).
[1] https://people.igalia.com/agomes/pdfium/samples/test_when_ap_use_rect.pdf
[2] https://people.igalia.com/agomes/pdfium/samples/test_when_no_ap_use_quadpoints.pdf